The estimation of the effect of recombinant interleukin -16 on T regulatory cells

Interleukin-16 (IL-16) is a protein secrected from a lot of immune and non-immune cells and its spesific effects on CD4+ T lymphocytes have been shown. Regulatory T cells (Tregs) are cells which prevent autoimmune diseases and the development of transplant rejections. They are also thought to have a role in the development of allergy and asthma. Tregs may control immune response by inhibiting the function of the other cells which have role in immune response. FoxP3 is a transcription factor which regulates the activation of Tregs. Our aim is to investigate the effects of IL-16 on the expression of FoxP3 which is the activation marker of Treg cells, cell apoptosis and cell death and to determine if there is a correlation between serum IL-16 levels and FoxP3 expression. For this purpose periferic mononuclear cells obtained from 30 healthy individuals were treated with IL-16 in vitro and FoxP3 levels shown to be increased by flow cytometric analysis. It has been also shown that IL-16 has no apoptotic or killing effect on Treg cells. On the other hand, apoptosis of 1% and death of 3% (approximately) of lymphocytes have been induced by IL-16. A positive correlation between serum IL-16 levels and Fox-P3 expression was found. In agreement with the literature, CD25 expression of Treg cells have shown to be increased. FoxP3 expression was found to be increased in the increased concentrations of IL-16. In conclusion this is the first in vivo study which shows the positive effect of IL-16 on FoxP3 expression. Investigation of IL-16 in diseases like atopy, allergy and autoimmunity in which immune system is insufficient or defected may contribute to the understanding of IL-16-disease and Treg-IL-16 relations.